1. Technical Field
The present invention relates to a system and method for providing access to the emergency services over a network, particularly a WiMAX network.
2. Background Art
WiMAX (Worldwide Interoperability for Microwave Access) is a standard established by the WiMAX Forum for providing wireless data over long distances. It is fast becoming an alternative to providing broadband Internet access over cable or DSL.
Currently, there are two forms of WiMAX, Fixed WiMAX and Mobile WiMAX. Fixed WiMAX is developed based on the IEEE 802.16-2004 (or 802.16d) standard and is optimized for fixed and nomadic applications in Line-of-Sight and Non-Line-of-Sight environments. Mobile WiMAX is based on the IEEE 802.16-2005 (or 802.16e) standard and targeted primarily for portable and mobile applications in a Non-Line-of-Sight environment, although Mobile WiMAX systems also can provide fixed and nomadic access. The IEEE 802.16e standard incorporates additional features necessary for mobile applications such as flexible power management (sleep mode and idle mode), channel bandwidth scalability (SOFDMA), fractional frequency reuse, and better Non-Line-of-Sight performance/indoor penetration.
The WiMAX device at the user end is known as the WiMAX Subscriber Station, WiMAX CPE (Customer Premises Equipment) or WiMAX MS (Mobile Station) and sends/receives data over the WiMAX network. A WiMAX device could, for example, be a PCMCIA card within a laptop, or a receiver box on the user's premises, which then relays data to the user's personal network.
A WiMAX network consists of an Access Service Network (ASN) and Connectivity Service Network (CSN). The WiMAX ASN is the combination of two logical components, the Base Station (BS) and ASN-Gateway, while the WiMAX CSN is a set of network functions that provide IP connectivity services to the WiMAX subscribers, such as connection to the Internet.
The WiMAX standard uses a connection-oriented MAC (Media Access Control) architecture, where all downlink and uplink connections are controlled by the serving Base Station. Before data transmission occurs, the Base Station and the Subscriber Station establish a connection between the two MAC-layer peers. Each connection is identified by a connection identifier (CID), which serves as a temporary address for user data transmissions over the links. To send or receive MAC management messages, the CIDs are used by the user or by the WiMAX network.
The connections are divided into two principle types-management and transport connections. Management connections carry management messages, whilst transport connections carry other traffic such as user data.
In the WiMAX standard there are three management connections, each with their own respective connection identifier. The three management connections are used to exchange control messages between the Base Station and Subscriber Station. They specify the different Quality of Service (QoS) requirements that are needed at the different management levels. The Basic connection is used to transfer short, time-critical MAC and Radio Link Control (RLC) messages. The Primary management connection transfers long and delay tolerant messages related to authentication and connection setup. The Secondary management connection is used to transfer standards-based messages like Dynamic Host Configuration Protocol (DHCP), Trivial File Transfer Protocol (TFTP) and Simple Network Management Protocol (SNMP).
The WiMAX standard also has a feature known as Service Flows. Service Flows are unidirectional flows of data with a particular set of parameters and data structure.
Each Service Flow is identified by Service Flow parameters, one of which is the Service Flow Identifier (SFID).
Currently, in WiMAX technology, there is no provision for a user to contact the emergency services, via a Subscriber Station, over a WiMAX network. The development of frameworks such as IMS for delivering IP multimedia services to end users has allowed the development of communication methods such a VoIP (Voice over IP), that allow users to communicate over networks such as the Internet.
One of the main issues for providing support for contacting the emergency services over a network is the location of the nearest Public Safety Answering Point (PSAP), which is a communication device used by the emergency services. All emergency calls are routed to the PSAP, which is the answering point of all emergency services and coordinates delivery of emergency calls to the proper emergency services such as Dolice, fire, etc.
If a reliable means to contact the emergency services is to be provided it is vital that users can do so via any WiMAX network, whether they are subscribed to the network or not. One problem with such a requirement is that, should a user not be registered with a particular WiMAX network, any attempt to contact the emergency services over the network would result in an authentication failure, as they are not authorized to use the network. This is even more important when dealing with mobile devices using the 802.16e standard, which may move between different networks frequently.